I think your friends should have gotten an e-mail with the flight changed information or if the flight was cancelled. You need to ask your friend if they got any contact from American with regards to the changed or cancelled flight.

I sign up for Flight Notifications and once I was booked on an itinerary where the partner carrier cancelled the flight and American sent me a notice of the change and I immediately called American and they switched me to an even better itinerary where I arrived at my destination earlier(which was my intention in the first place but the cost of the flight was more expensive).

So American booked me on an earlier flight with their partner that would cost me more and even got me seats at the front of the cabin for no additional charge and was good to go. The ticket was reticketed within the hour and I got the updated itinerary.

A really painless process and I even was able to ask American to extend the return for a few days later with no change fee due to the change in itinerary my Fare Code allowed for this and they waived the change fee. So I got to stay at my destination longer.

A Win Win in my book(: